tracing: Add support for recording tgid of tasks

Inorder to support recording of tgid, the following changes are made:

* Introduce a new API (tracing_record_taskinfo) to additionally record the tgid
  along with the task's comm at the same time. This has has the benefit of not
  setting trace_cmdline_save before all the information for a task is saved.
* Add a new API tracing_record_taskinfo_sched_switch to record task information
  for 2 tasks at a time (previous and next) and use it from sched_switch probe.
* Preserve the old API (tracing_record_cmdline) and create it as a wrapper
  around the new one so that existing callers aren't affected.
* Reuse the existing sched_switch and sched_wakeup probes to record tgid
  information and add a new option 'record-tgid' to enable recording of tgid

When record-tgid option isn't enabled to being with, we take care to make sure
that there's isn't memory or runtime overhead.

Link: http://lkml.kernel.org/r/20170627020155.5139-1-joelaf@google.com
Cc: kernel-team@android.com
Cc: Ingo Molnar <mingo@redhat.com>
Tested-by: Michael Sartain <mikesart@gmail.com>
Signed-off-by: Joel Fernandes <joelaf@google.com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>

diff --git a/include/linux/trace_events.h b/include/linux/trace_events.h
index a556805..f73cedf 100644 (file)
--- a/include/linux/trace_events.h
+++ b/include/linux/trace_events.h
@@ -151,7 +151,15 @@ trace_event_buffer_lock_reserve(struct ring_buffer **current_buffer,
                                int type, unsigned long len,
                                unsigned long flags, int pc);
 
-void tracing_record_cmdline(struct task_struct *tsk);
+#define TRACE_RECORD_CMDLINE   BIT(0)
+#define TRACE_RECORD_TGID      BIT(1)
+
+void tracing_record_taskinfo(struct task_struct *task, int flags);
+void tracing_record_taskinfo_sched_switch(struct task_struct *prev,
+                                         struct task_struct *next, int flags);
+
+void tracing_record_cmdline(struct task_struct *task);
+void tracing_record_tgid(struct task_struct *task);
 
 int trace_output_call(struct trace_iterator *iter, char *name, char *fmt, ...);
 
@@ -290,6 +298,7 @@ struct trace_subsystem_dir;
 enum {
        EVENT_FILE_FL_ENABLED_BIT,
        EVENT_FILE_FL_RECORDED_CMD_BIT,
+       EVENT_FILE_FL_RECORDED_TGID_BIT,
        EVENT_FILE_FL_FILTERED_BIT,
        EVENT_FILE_FL_NO_SET_FILTER_BIT,
        EVENT_FILE_FL_SOFT_MODE_BIT,
@@ -303,6 +312,7 @@ enum {
  * Event file flags:
  *  ENABLED      - The event is enabled
  *  RECORDED_CMD  - The comms should be recorded at sched_switch
+ *  RECORDED_TGID - The tgids should be recorded at sched_switch
  *  FILTERED     - The event has a filter attached
  *  NO_SET_FILTER - Set when filter has error and is to be ignored
  *  SOFT_MODE     - The event is enabled/disabled by SOFT_DISABLED
@@ -315,6 +325,7 @@ enum {
 enum {
        EVENT_FILE_FL_ENABLED           = (1 << EVENT_FILE_FL_ENABLED_BIT),
        EVENT_FILE_FL_RECORDED_CMD      = (1 << EVENT_FILE_FL_RECORDED_CMD_BIT),
+       EVENT_FILE_FL_RECORDED_TGID     = (1 << EVENT_FILE_FL_RECORDED_TGID_BIT),
        EVENT_FILE_FL_FILTERED          = (1 << EVENT_FILE_FL_FILTERED_BIT),
        EVENT_FILE_FL_NO_SET_FILTER     = (1 << EVENT_FILE_FL_NO_SET_FILTER_BIT),
        EVENT_FILE_FL_SOFT_MODE         = (1 << EVENT_FILE_FL_SOFT_MODE_BIT),

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 14318ce..ab9db75 100644 (file)
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -87,7 +87,7 @@ dummy_set_flag(struct trace_array *tr, u32 old_flags, u32 bit, int set)
  * tracing is active, only save the comm when a trace event
  * occurred.
  */
-static DEFINE_PER_CPU(bool, trace_cmdline_save);
+static DEFINE_PER_CPU(bool, trace_taskinfo_save);
 
 /*
  * Kill all tracing for good (never come back).
@@ -790,7 +790,7 @@ EXPORT_SYMBOL_GPL(tracing_on);
 static __always_inline void
 __buffer_unlock_commit(struct ring_buffer *buffer, struct ring_buffer_event *event)
 {
-       __this_cpu_write(trace_cmdline_save, true);
+       __this_cpu_write(trace_taskinfo_save, true);
 
        /* If this is the temp buffer, we need to commit fully */
        if (this_cpu_read(trace_buffered_event) == event) {
@@ -1709,6 +1709,8 @@ void tracing_reset_all_online_cpus(void)
        }
 }
 
+static int *tgid_map;
+
 #define SAVED_CMDLINES_DEFAULT 128
 #define NO_CMDLINE_MAP UINT_MAX
 static arch_spinlock_t trace_cmdline_lock = __ARCH_SPIN_LOCK_UNLOCKED;
@@ -1722,7 +1724,7 @@ struct saved_cmdlines_buffer {
 static struct saved_cmdlines_buffer *savedcmd;
 
 /* temporary disable recording */
-static atomic_t trace_record_cmdline_disabled __read_mostly;
+static atomic_t trace_record_taskinfo_disabled __read_mostly;
 
 static inline char *get_saved_cmdlines(int idx)
 {
@@ -1990,16 +1992,87 @@ void trace_find_cmdline(int pid, char comm[])
        preempt_enable();
 }
 
-void tracing_record_cmdline(struct task_struct *tsk)
+int trace_find_tgid(int pid)
+{
+       if (unlikely(!tgid_map || !pid || pid > PID_MAX_DEFAULT))
+               return 0;
+
+       return tgid_map[pid];
+}
+
+static int trace_save_tgid(struct task_struct *tsk)
 {
-       if (atomic_read(&trace_record_cmdline_disabled) || !tracing_is_on())
+       if (unlikely(!tgid_map || !tsk->pid || tsk->pid > PID_MAX_DEFAULT))
+               return 0;
+
+       tgid_map[tsk->pid] = tsk->tgid;
+       return 1;
+}
+
+static bool tracing_record_taskinfo_skip(int flags)
+{
+       if (unlikely(!(flags & (TRACE_RECORD_CMDLINE | TRACE_RECORD_TGID))))
+               return true;
+       if (atomic_read(&trace_record_taskinfo_disabled) || !tracing_is_on())
+               return true;
+       if (!__this_cpu_read(trace_taskinfo_save))
+               return true;
+       return false;
+}
+
+/**
+ * tracing_record_taskinfo - record the task info of a task
+ *
+ * @task  - task to record
+ * @flags - TRACE_RECORD_CMDLINE for recording comm
+ *        - TRACE_RECORD_TGID for recording tgid
+ */
+void tracing_record_taskinfo(struct task_struct *task, int flags)
+{
+       if (tracing_record_taskinfo_skip(flags))
+               return;
+       if ((flags & TRACE_RECORD_CMDLINE) && !trace_save_cmdline(task))
+               return;
+       if ((flags & TRACE_RECORD_TGID) && !trace_save_tgid(task))
                return;
 
-       if (!__this_cpu_read(trace_cmdline_save))
+       __this_cpu_write(trace_taskinfo_save, false);
+}
+
+/**
+ * tracing_record_taskinfo_sched_switch - record task info for sched_switch
+ *
+ * @prev - previous task during sched_switch
+ * @next - next task during sched_switch
+ * @flags - TRACE_RECORD_CMDLINE for recording comm
+ *          TRACE_RECORD_TGID for recording tgid
+ */
+void tracing_record_taskinfo_sched_switch(struct task_struct *prev,
+                                         struct task_struct *next, int flags)
+{
+       if (tracing_record_taskinfo_skip(flags))
                return;
 
-       if (trace_save_cmdline(tsk))
-               __this_cpu_write(trace_cmdline_save, false);
+       if ((flags & TRACE_RECORD_CMDLINE) &&
+           (!trace_save_cmdline(prev) || !trace_save_cmdline(next)))
+               return;
+
+       if ((flags & TRACE_RECORD_TGID) &&
+           (!trace_save_tgid(prev) || !trace_save_tgid(next)))
+               return;
+
+       __this_cpu_write(trace_taskinfo_save, false);
+}
+
+/* Helpers to record a specific task information */
+void tracing_record_cmdline(struct task_struct *task)
+{
+       tracing_record_taskinfo(task, TRACE_RECORD_CMDLINE);
+}
+
+void tracing_record_tgid(struct task_struct *task)
+{
+       tracing_record_taskinfo(task, TRACE_RECORD_TGID);
 }
 
 /*
@@ -3144,7 +3217,7 @@ static void *s_start(struct seq_file *m, loff_t *pos)
 #endif
 
        if (!iter->snapshot)
-               atomic_inc(&trace_record_cmdline_disabled);
+               atomic_inc(&trace_record_taskinfo_disabled);
 
        if (*pos != iter->pos) {
                iter->ent = NULL;
@@ -3189,7 +3262,7 @@ static void s_stop(struct seq_file *m, void *p)
 #endif
 
        if (!iter->snapshot)
-               atomic_dec(&trace_record_cmdline_disabled);
+               atomic_dec(&trace_record_taskinfo_disabled);
 
        trace_access_unlock(iter->cpu_file);
        trace_event_read_unlock();
@@ -4236,6 +4309,18 @@ int set_tracer_flag(struct trace_array *tr, unsigned int mask, int enabled)
        if (mask == TRACE_ITER_RECORD_CMD)
                trace_event_enable_cmd_record(enabled);
 
+       if (mask == TRACE_ITER_RECORD_TGID) {
+               if (!tgid_map)
+                       tgid_map = kzalloc((PID_MAX_DEFAULT + 1) * sizeof(*tgid_map),
+                                          GFP_KERNEL);
+               if (!tgid_map) {
+                       tr->trace_flags &= ~TRACE_ITER_RECORD_TGID;
+                       return -ENOMEM;
+               }
+
+               trace_event_enable_tgid_record(enabled);
+       }
+
        if (mask == TRACE_ITER_EVENT_FORK)
                trace_event_follow_fork(tr, enabled);
 

diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
index 1382395..6ade1c5 100644 (file)
--- a/kernel/trace/trace.h
+++ b/kernel/trace/trace.h
@@ -640,6 +640,9 @@ void set_graph_array(struct trace_array *tr);
 
 void tracing_start_cmdline_record(void);
 void tracing_stop_cmdline_record(void);
+void tracing_start_tgid_record(void);
+void tracing_stop_tgid_record(void);
+
 int register_tracer(struct tracer *type);
 int is_tracing_stopped(void);
 
@@ -700,6 +703,7 @@ static inline void __trace_stack(struct trace_array *tr, unsigned long flags,
 extern u64 ftrace_now(int cpu);
 
 extern void trace_find_cmdline(int pid, char comm[]);
+extern int trace_find_tgid(int pid);
 extern void trace_event_follow_fork(struct trace_array *tr, bool enable);
 
 #ifdef CONFIG_DYNAMIC_FTRACE
@@ -1124,6 +1128,7 @@ extern int trace_get_user(struct trace_parser *parser, const char __user *ubuf,
                C(CONTEXT_INFO,         "context-info"),   /* Print pid/cpu/time */ \
                C(LATENCY_FMT,          "latency-format"),      \
                C(RECORD_CMD,           "record-cmd"),          \
+               C(RECORD_TGID,          "record-tgid"),         \
                C(OVERWRITE,            "overwrite"),           \
                C(STOP_ON_FREE,         "disable_on_free"),     \
                C(IRQ_INFO,             "irq-info"),            \
@@ -1440,6 +1445,8 @@ struct ftrace_event_field *
 trace_find_event_field(struct trace_event_call *call, char *name);
 
 extern void trace_event_enable_cmd_record(bool enable);
+extern void trace_event_enable_tgid_record(bool enable);
+
 extern int event_trace_add_tracer(struct dentry *parent, struct trace_array *tr);
 extern int event_trace_del_tracer(struct trace_array *tr);
 

diff --git a/kernel/trace/trace_events.c b/kernel/trace/trace_events.c
index 83dfd0d..36132f9 100644 (file)
--- a/kernel/trace/trace_events.c
+++ b/kernel/trace/trace_events.c
@@ -343,6 +343,28 @@ void trace_event_enable_cmd_record(bool enable)
        mutex_unlock(&event_mutex);
 }
 
+void trace_event_enable_tgid_record(bool enable)
+{
+       struct trace_event_file *file;
+       struct trace_array *tr;
+
+       mutex_lock(&event_mutex);
+       do_for_each_event_file(tr, file) {
+               if (!(file->flags & EVENT_FILE_FL_ENABLED))
+                       continue;
+
+               if (enable) {
+                       tracing_start_tgid_record();
+                       set_bit(EVENT_FILE_FL_RECORDED_TGID_BIT, &file->flags);
+               } else {
+                       tracing_stop_tgid_record();
+                       clear_bit(EVENT_FILE_FL_RECORDED_TGID_BIT,
+                                 &file->flags);
+               }
+       } while_for_each_event_file();
+       mutex_unlock(&event_mutex);
+}
+
 static int __ftrace_event_enable_disable(struct trace_event_file *file,
                                         int enable, int soft_disable)
 {
@@ -381,6 +403,12 @@ static int __ftrace_event_enable_disable(struct trace_event_file *file,
                                tracing_stop_cmdline_record();
                                clear_bit(EVENT_FILE_FL_RECORDED_CMD_BIT, &file->flags);
                        }
+
+                       if (file->flags & EVENT_FILE_FL_RECORDED_TGID) {
+                               tracing_stop_tgid_record();
+                               clear_bit(EVENT_FILE_FL_RECORDED_CMD_BIT, &file->flags);
+                       }
+
                        call->class->reg(call, TRACE_REG_UNREGISTER, file);
                }
                /* If in SOFT_MODE, just set the SOFT_DISABLE_BIT, else clear it */
@@ -407,18 +435,30 @@ static int __ftrace_event_enable_disable(struct trace_event_file *file,
                }
 
                if (!(file->flags & EVENT_FILE_FL_ENABLED)) {
+                       bool cmd = false, tgid = false;
 
                        /* Keep the event disabled, when going to SOFT_MODE. */
                        if (soft_disable)
                                set_bit(EVENT_FILE_FL_SOFT_DISABLED_BIT, &file->flags);
 
                        if (tr->trace_flags & TRACE_ITER_RECORD_CMD) {
+                               cmd = true;
                                tracing_start_cmdline_record();
                                set_bit(EVENT_FILE_FL_RECORDED_CMD_BIT, &file->flags);
                        }
+
+                       if (tr->trace_flags & TRACE_ITER_RECORD_TGID) {
+                               tgid = true;
+                               tracing_start_tgid_record();
+                               set_bit(EVENT_FILE_FL_RECORDED_TGID_BIT, &file->flags);
+                       }
+
                        ret = call->class->reg(call, TRACE_REG_REGISTER, file);
                        if (ret) {
-                               tracing_stop_cmdline_record();
+                               if (cmd)
+                                       tracing_stop_cmdline_record();
+                               if (tgid)
+                                       tracing_stop_tgid_record();
                                pr_info("event trace: Could not enable event "
                                        "%s\n", trace_event_name(call));
                                break;

diff --git a/kernel/trace/trace_sched_switch.c b/kernel/trace/trace_sched_switch.c
index 4c896a0..b341c02 100644 (file)
--- a/kernel/trace/trace_sched_switch.c
+++ b/kernel/trace/trace_sched_switch.c
@@ -12,27 +12,38 @@
 
 #include "trace.h"
 
-static int                     sched_ref;
+#define RECORD_CMDLINE 1
+#define RECORD_TGID    2
+
+static int             sched_cmdline_ref;
+static int             sched_tgid_ref;
 static DEFINE_MUTEX(sched_register_mutex);
 
 static void
 probe_sched_switch(void *ignore, bool preempt,
                   struct task_struct *prev, struct task_struct *next)
 {
-       if (unlikely(!sched_ref))
-               return;
+       int flags;
+
+       flags = (RECORD_TGID * !!sched_tgid_ref) +
+               (RECORD_CMDLINE * !!sched_cmdline_ref);
 
-       tracing_record_cmdline(prev);
-       tracing_record_cmdline(next);
+       if (!flags)
+               return;
+       tracing_record_taskinfo_sched_switch(prev, next, flags);
 }
 
 static void
 probe_sched_wakeup(void *ignore, struct task_struct *wakee)
 {
-       if (unlikely(!sched_ref))
-               return;
+       int flags;
+
+       flags = (RECORD_TGID * !!sched_tgid_ref) +
+               (RECORD_CMDLINE * !!sched_cmdline_ref);
 
-       tracing_record_cmdline(current);
+       if (!flags)
+               return;
+       tracing_record_taskinfo(current, flags);
 }
 
 static int tracing_sched_register(void)
@@ -75,28 +86,61 @@ static void tracing_sched_unregister(void)
        unregister_trace_sched_wakeup(probe_sched_wakeup, NULL);
 }
 
-static void tracing_start_sched_switch(void)
+static void tracing_start_sched_switch(int ops)
 {
+       bool sched_register = (!sched_cmdline_ref && !sched_tgid_ref);
        mutex_lock(&sched_register_mutex);
-       if (!(sched_ref++))
+
+       switch (ops) {
+       case RECORD_CMDLINE:
+               sched_cmdline_ref++;
+               break;
+
+       case RECORD_TGID:
+               sched_tgid_ref++;
+               break;
+       }
+
+       if (sched_register && (sched_cmdline_ref || sched_tgid_ref))
                tracing_sched_register();
        mutex_unlock(&sched_register_mutex);
 }
 
-static void tracing_stop_sched_switch(void)
+static void tracing_stop_sched_switch(int ops)
 {
        mutex_lock(&sched_register_mutex);
-       if (!(--sched_ref))
+
+       switch (ops) {
+       case RECORD_CMDLINE:
+               sched_cmdline_ref--;
+               break;
+
+       case RECORD_TGID:
+               sched_tgid_ref--;
+               break;
+       }
+
+       if (!sched_cmdline_ref && !sched_tgid_ref)
                tracing_sched_unregister();
        mutex_unlock(&sched_register_mutex);
 }
 
 void tracing_start_cmdline_record(void)
 {
-       tracing_start_sched_switch();
+       tracing_start_sched_switch(RECORD_CMDLINE);
 }
 
 void tracing_stop_cmdline_record(void)
 {
-       tracing_stop_sched_switch();
+       tracing_stop_sched_switch(RECORD_CMDLINE);
+}
+
+void tracing_start_tgid_record(void)
+{
+       tracing_start_sched_switch(RECORD_TGID);
+}
+
+void tracing_stop_tgid_record(void)
+{
+       tracing_stop_sched_switch(RECORD_TGID);
 }